In many cases, a torque converter is provided with a lock-up device for directly transmitting torque from a front cover to a turbine. The lock-up device includes: a piston that can be frictionally coupled to the front cover; a drive plate fixed to the piston; a plurality of torsion springs supported by the drive plate; and a driven plate elastically coupled to the piston by the plural torsion springs in the rotational direction. The driven plate is fixed to the turbine.
Further, a lock-up device of so-called a multi-plate type using a plurality of clutch plates has been already proposed for increasing the clutch capacity in the lock-up device (see PTL 1).
When torque is herein transmitted by the lock-up device, reduction in stiffness and expansion in a torsion angle are required for the torsion springs in order to effectively absorb and attenuate variation in torque inputted thereto from an engine. In view of this, such a device as described in PTL 2 has been proposed. Pairs of torsion springs, composing a damper mechanism, herein act in series through an intermediate member.